1. Field of the Invention
This invention relates to the structure and fabrication of end closure modules for coupling to and enclosure of tanks and vessel bodies. More particularly, this invention relates to end closure modules for coupling to and enclosure of multi-cell tanks and vessel bodies, especially tanks and vessels suitable for storing liquid propane.
2. Description of the Related Art
Pressure vessels are widely known for storing liquids and gases under pressure. One growing application of pressure vessels is their use in the storage of alternative fuels, such as propane and natural gas, for use in vehicles such as automobiles. Alternative fuels are increasingly being viewed as preferable to gasoline for fueling vehicles. Accordingly, approaches have been devised for converting gasoline-fueled vehicles to propane-fueled vehicles by retrofitting the gasoline-fueled vehicles to use propane (or natural gas) instead of gasoline. Vehicles are currently being built which are designed to operate using propane (or natural gas) as their fuel source.
Typical storage tanks are cylindrical in shape. Positioning cylindrical storage tanks in the envelope utilized for a fuel tank in most vehicles results in substantial limitations in the amount of propane or natural gas a vehicle can carry. Hence, storage tanks have been devised which utilize a plurality of arcuate outer wall segments that are connected by internal web segments to form a multi-cell pressure vessel. Such multi-cell pressure vessels have a generally uniform cross section, thereby enabling the outer wall segments to be formed by extrusion.
A multi-cell pressure vessel body especially advantageous for storage of compressed natural gas or liquid propane disclosed in PCT US97/15116 (WO 98/09876), the complete disclosure of which is incorporated by reference. This preferred vessel body structure is depicted in FIGS. 4-7 herein and discussed in greater detail below.
One disadvantage associated with multi-cell pressure vessels is the difficulty of obtaining a secure and inexpensive joint for connecting end closures to the body structure of the pressure vessel. Conventionally, dome closures of multi-cell pressure vessels have been constructed as depicted in FIG. 8. Referring to FIG. 8, dome segments 802 are fabricated from standard stamped or spun material, with the dome segments 802 being coupled together at mating joints. Internal reinforcement ribs 804 are provided at the joints of the dome sections to carry internal pressures. Typically, the dome segments 802 are coupled together and to the internal reinforcement ribs 804 by welding. This technique permits for a variety of dome structures to be fabricated; however, the use of welded joints and separate dome segments 802 and ribs 804 increases manufacturing costs and time.
One-piece domes partially eliminate the problems associated with welding dome segments to each other and to internal reinforcement ribs. An example of a one-piece dome having reinforcing ribs is illustrated in FIG. 9 and designated by reference numeral 900. However, expensive tooling is required to stamp one-piece domes. Further, conventional tooling for stamping one-piece domes is capable of forming domes for only one tank size. Thus, different stamp toolings must be provided for making tanks of different sizes and shapes. Additionally, the one-piece dome embodiment still requires the manual welding of reinforcement ribs 904 inside the dome for imparting reinforcing strength.
It would, therefore, be a significant advancement in the art to provide a set of end dome structures for a multi-cell vessel that would be inexpensive to manufacture and assemble in a variety of arrangements, yet is not prone to significant losses in strength such as those which arise from exposure to heat during conventional welding techniques.
It is, therefore, an object of this invention to provide a set of closure modules of an end closure structure for a multi-cell pressure vessel that attains the above-discussed advancement in the art.
Generally, the body portion of a multi-cell pressure vessel comprises a plurality of arcuate outer wall segments connected by internal web segments. Most, if not all of the cells are individually defined by a combination of at least one internal web segment and at least one arcuate outer wall segment. Optionally, for cases in which the body portion is defined by more than two rows and more than two columns of cells, some of the internal cells of the multi-cell pressure vessel can be individually defined by a combination of internal web segments, but not arcuate outer wall segments.
Each of the cells defines a cell chamber and terminates at opposite ends thereof to define respective cell chamber openings. Each of the cell chamber openings is thereby defined at a periphery thereof by edges of either a combination of at least one internal web segment and at least one arcuate outer wall segment or, for internal cells defined by internal web segment but not arcuate outer wall segments, a combination of internal web segments.
A first end closure module and a second end closure module each comprises an arcuate surface portion and at least one interfacing surface portion. The interfacing surface portion has a marginal extent integrally connected with a marginal extent of the arcuate surface portion. The inner surfaces of the arcuate surface portion and the interfacing surface portion, collectively or in combination with at least one additional interfacing surface portion of the end closure modules, define a closure module chamber associated with a closure module opening. The closure module opening is defined at a periphery thereof by free edges of the arcuate surface portion and the interfacing surface portion or free edges of the arcuate surface portion, the interfacing surface portion, and the additional interfacing surface portion. For modules associated with internal cells defined by internal web segments but not arcuate outer wall segments, however, the closure module opening is defined at its periphery by a combination of interfacing surface portions. In the preferred embodiment illustrated in the drawings, the interfacing surface portions are planar.
Optionally, joggles or rims can be formed about respective closure module openings and constructed and arranged to be inserted into and coupled to ends of associated cells, so that the closure modules cooperate with their associated cells to close the ends of the associated cell chambers. The interfacing surface portion of the first closure module is constructed and arranged to lie contiguously against the interfacing surface of the adjacent second closure module, thereby facilitating the coupling of the adjacent first and second closure modules to each other. The respective interfacing surface portions of the adjacent first and second closure modules can be coupled by coupling the set of closure modules to ends of their respective associated cells. Additionally or in the alternative, the interfacing surfaces of the adjacent first and second closure modules can be welded, brazed, fastened or otherwise coupled together.
It is another object of this invention to provide a multi-cell pressure vessel comprising a multi-cell vessel body and one or more of the above-discussed sets of closure modules. The multi-cell pressure vessel of this invention can be installed (as original or retrofitted parts) by techniques known to those of ordinary skill in the art in various kinds of vehicles, including, by way of example, cars, trucks, vans, sport utility vehicles, military vehicles, recreational vehicles, aircraft, and boats and ships.
According to an aspect of the invention, the multi-cell pressure vessel comprises a body portion comprising a plurality of arcuate outer wall segments connected by internal web segments that collectively define a plurality of cells and terminate at ends thereof to define peripheries of cell chamber openings. The vessel also comprises a set of closure modules, with each closure module of the set of closure modules closing an associated end of a respective one of the cells at a respective one of the cell chamber openings. The set of closure modules includes a first closure module and a second closure module. Each of the first and second closure modules comprises, respectively, an arcuate surface portion having an inner surface and an interfacing surface portion having an inner surface, an outer surface opposite to the inner surface, and a marginal extent. The inner and outer surfaces are preferably planar. The marginal extent of the interfacing surface portion is integrally connected with a marginal extent of the arcuate surface portion. The inner surface of the arcuate surface portion and the planar inner surface of the interfacing surface portion define, collectively or in combination with at least one additional interfacing surface portion, a closure module chamber with a closure module opening. The closure module opening is defined at a periphery thereof by either free edges of the arcuate surface portion and the interfacing surface portion or free edges of the arcuate surface portion, the interfacing surface portion, and the at least one additional interfacing surface portion. The planar outer surface of the interfacing surface portion of the first closure module abuts contiguously against and is coupled with the planar outer surface of the interfacing surface portion of the second closure module. Preferably, these abutting interfacing surface portions are oriented parallel to the internal web segments.
Other objects, aspects and advantages of the invention will be apparent to those skilled in the art upon reading the specification and appended claims which, when read in conjunction with the accompanying drawings, explain the principles of this invention.